JP2008021495A - Heating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating apparatus of which moldability of an induction heating coil is improved, with a heating efficiency improved, as well. <P>SOLUTION: An induction heating coil for induction-heating an object consists of a first litz wire 39b, in which a plurality of wires 39a having an insulating layer on a conductor, are stranded, and a second litz wire 39 in which a plurality of first litz wires 39b are stranded. The number of first litz wires 39b, forming the second litz wire 39 is larger than that of the wires 39a, constituting the first litz wire 39b. So, disconnection of the wires 39a, when forming the first litz wire 39b is prevented for improved moldability of an induction heating coil and for improved heating efficiency as an apparatus. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heating device provided with an induction heating coil such as a rice cooker used for general household or business use.

  Conventionally, as an induction heating coil in this kind of heating device, a first litz wire formed by twisting a plurality of strands having an insulating layer on a conductor and two or more first litz wires are twisted together. A second litz wire formed in the manner described above is known (for example, see Patent Document 1).

This is because the distance from the surface of the conductor portion to the center is shortened by setting the diameter of the conductor portion of the strand to 0.4 mm or less. When a high-frequency current flows through the conductor, the skin effect that the current flows in a concentrated manner on the surface layer of the conductor reduces the diameter of the strand conductor portion and increases the number of strands to obtain a predetermined surface area. The self-heating of the pot is suppressed and the heating efficiency to the pan as the object to be heated is improved.
JP-A-6-260270

  However, in the above-described conventional configuration, in order to maximize the skin effect of the induction heating coil, it is necessary to reduce the diameter of the strands constituting the first litz wire and increase the number of strands. However, if the wire diameter of the strands is reduced, the skin effect can be obtained efficiently, but the first and second litz wires are formed by twisting the strands and the first litz wires. If the wire was too thin, it could break.

  It is also known that when a high-frequency current is applied to an electric wire, a skin effect occurs, and when the wires are twisted together, there is an effect of a proximity effect that is contrary to the skin effect. By reducing the wire diameter of the strands forming the first litz wire, the gap between the first litz wires is reduced, and further, the gap between the first litz wires constituting the second litz wire is reduced. If it is too much, the skin effect can be obtained, but conversely, the influence of the proximity effect is also large, and the effective resistance value as the induction heating coil increases, leading to a decrease in heating efficiency.

  This invention solves the said conventional subject, and it aims at providing the heating apparatus which can also improve the heating efficiency while improving the moldability of an induction heating coil.

  In order to solve the conventional problem, the heating device of the present invention includes an induction heating coil for induction heating of an object to be heated, and the induction heating coil twists a plurality of strands having an insulating layer on a conductor. The first litz wire is formed by the combined first litz wire and the second litz wire formed by twisting a plurality of the first litz wires, and the first litz wire number forming the second litz wire. The number of strands constituting the line is increased.

  Thereby, disconnection of the strand at the time of forming a 1st litz wire can be prevented, the moldability of an induction heating coil can be improved, and the heating efficiency as an apparatus can be improved.

  The heating device of the present invention can improve the moldability of the induction heating coil and can improve the heating efficiency as the device.

  1st invention is equipped with the induction heating coil for induction-heating an to-be-heated material, and the said induction heating coil is 1st litz wire which twisted together the strand which has an insulating layer on a conductor, 1st The second litz wire is formed by twisting a plurality of litz wires, and the number of strands constituting the first litz wire is larger than the number of first litz wires forming the second litz wire. By setting it as an apparatus, disconnection of the strand at the time of forming a 1st litz wire can be prevented, the moldability of an induction heating coil can be improved, and the heating efficiency as an apparatus can be improved.

  In the second invention, in particular, in the first invention, the induction heating coil has a spiral shape and is disposed so as to oppose the bottom portion of the pan and the side surface portion of the pan bottom to be heated. Convection of objects can be efficiently performed throughout the pan.

  The third invention is that, in the second invention, in particular, the induction heating coil has a smaller number of turns of the induction heating coil facing the pan bottom side than the number of turns of the induction heating coil facing the bottom of the pot. Thereby, the heating of the pan bottom center side can be increased.

  According to a fourth aspect of the invention, in particular, in the second or third aspect of the invention, the induction heating coil is thinner in thickness than the induction heating coil facing the bottom of the pan than the thickness of the induction heating coil facing the pan bottom side. As a result, the induction heating coil can wind more induction heating coils on the center side of the pan bottom than the induction heating coil on the side surface of the pan bottom for a certain width, and can increase heating on the center side of the pan.

  In particular, the fifth invention is the induction heating coil according to any one of the second to fourth inventions, wherein the induction heating coil is formed in a spiral shape by overlapping a plurality of stages, so that the induction heating coil is not changed without changing the core wire configuration. The number of turns of the coil can be freely determined within a certain width.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment)
The figure illustrates a rice cooker as a heating device in the embodiment of the present invention.

  In FIG. 1, the device main body 31 has a substantially cylindrical shape with an upper surface opened, and an upper frame 32 is fitted into the opening of the device main body 31. Inside the device main body 31, an upper frame 32 and a coil base 33 form a storage portion for a pot 34 that is an object to be heated. The coil base 33 is formed in a bottomed cylindrical shape, and the upper end portion of the coil base 33 is fixed to the upper frame 32. The coil base 33 is provided with an induction heating coil 35 for induction heating of the pot 34, and the pot 34 is induction heated. In the induction heating coil 35, a bottom induction heating coil 35 a is installed at the bottom of the pan 34, and a side induction coil 35 b is installed on the side of the pan bottom of the pan 34. In addition, a bottom sensor 36 for detecting the temperature of the pan 34 is energized by a sensor spring (not shown) at the center of the bottom of the pan 34 to detect the temperature of the pot when cooking and keeping warm, and the food in the pan 34 (rice + Water) is controlled to reach an optimum temperature state.

  The outer lid 37 is made of synthetic resin, and the outer lid 37 is fitted to the outer lid cover 38. A hinge shaft 32a is integrally formed at the rear portion of the upper frame 32 with a hinge shaft installed on the outer lid cover 38. It is rotatably supported via a pin.

  Here, the induction heating coil 35 will be described in detail with reference to FIG.

  The induction heating coil 35 includes a first litz wire 39b obtained by twisting 24 strands 39a having an outer diameter of φ0.1 mm having an insulating layer on a conductor at a pitch of 30 mm, and 16 first litz wires 39b. The second litz wire 39 is twisted at a pitch of 100 mm. Further, the induction heating coil 35 is spirally formed by winding the second litz wire 39 in a spiral shape. The induction heating coil 35 has a shape that follows the shape of the bottom of the pan 34, and the bottom induction heating coil 35 a and the side induction heating coil 35 b are installed at positions facing the pan 34.

  Further, the bottom induction heating coil 35a of the induction heating coil 35 has a width of 39 mm, a thickness of 3.3 mm, a winding number of 17 turns, and the side induction heating coil 35b has a width of 28 mm, a thickness of 2.4 mm, and a winding number of 10 turns. It is configured.

  What should be noted is the thickness and the number of turns of the bottom induction heating coil 35a and the side induction heating coil 35b. Looking at the coil thickness, as shown in FIG. 4, the thickness B of the side induction heating coil 35b is thinner than the thickness A of the bottom induction heating coil 35a. A thick coil means that a large number of turns can be secured with a constant width. When the bottom induction heating coil 35 a and the side induction heating coil 35 b are connected in series, the heat generated in the pan 34 is proportional to the distance between the pan 34 and the induction heating coil 35 and the number of turns of the induction heating coil 35. By increasing the thickness of the bottom induction heating coil 35a and securing a large number of turns in a certain width, the bottom center portion of the pan 34 can generate more heat than the side portion.

  As the temperature of the cooked rice is made uniform, the cooking unevenness can be reduced, and the cooking performance is improved. However, even with induction heating in which the pan 34 generates heat, the heating generates heat only on the surface of the pan 34. For this reason, in order to keep the temperature in the pan 34 constant, keeping the temperature in the pan 34 uniform by causing convection of the cooked food is considered as the basis of rice cooking. Here, looking at the convection that occurs in the pan 34, the portion of the pan 34 where the induction heating coil 35 is installed generates heat, so that the temperature of the cooked food in that portion rises, and the cook is upward. Although the low-temperature cooked food is lowered downward, the cooked food is heated along the shape of the pan 34, so that the side surface of the pan 34 easily moves upward along the side shape of the pan 34. .

  However, since the bottom of the pan 34 is substantially horizontal at the center of the bottom of the pan, it is difficult to move upward away from the bottom of the pan 34. This is apparent from the manner of generation of bubbles (water vapor) in the initial stage of boiling of the pan 34. The generated bubbles easily rise along the side of the pan 34 while the bubbles on the side of the pan 34 rise easily. It is a small amount that the bubbles move away from the surface of the pan 34 and move upward. For this reason, when the bottom face part and the side part of the pan 34 have the same calorific value, the convection on the side face of the pan 34 is promoted, and the convection at the center part of the pan 34 is difficult to occur. For this reason, the temperature difference of a cooking material will be made in the pan 34 side surface and the pan 34 center. It will cause uneven cooking. For this reason, it is necessary to change the calorific value of the bottom surface of the pan 34 and the side surface of the pan 34 to increase the heat generation on the bottom surface side of the pan 34.

  In this way, in order to freely bring out the shape of the induction heating coil 35, the wire 39a of the induction heating coil 35 is provided with an insulating layer on the outer periphery of the conductive portion, and a fusion layer is provided on the outer side of the insulating layer. The first litz wire 39b is formed by twisting a plurality of strands 39a, and the second litz wire 39 is formed by twisting a plurality of the first litz wires 39b. In order to stabilize the shape of the coil 35, the fusion layers are bonded together to stabilize the shape.

  For this reason, by making the gap between the strands 39a and the first litz wire 39b as small as possible, the adhesion portion of the fusion layer increases, and the shape becomes more stable. Further, reducing the gap between the strands 39a not only stabilizes the shape of the induction heating coil 35, but also increases the surface area of the second litz wire 39.

  When a high-frequency current is passed through the strands, current flows on the surface of the strands due to the skin effect of the strands, increasing the effective resistance. Therefore, make the induction heating coil as thin as possible and use multiple wires. By forming the wire with a wire, the cross-sectional area of the induction heating coil is increased and the efficiency of the device is improved. However, as described above, the effect when the induction heating coil 35 is formed by twisting the strands is the skin effect and the proximity effect. Among them, the proximity effect is that when a plurality of strands are twisted and a high-frequency current is passed, the concentric coupling of the strands is increased due to the influence of the current flowing on the surface of the strands, and the effective resistance value of the induction heating coil 35 is increased. This is an effect. For this reason, the induction heating coil 35 needs to be configured in consideration of both the skin effect and the proximity effect.

  Here, looking at the induction heating coil 35, the first litz wire 39b is formed by twisting 24 strands 39a, and the first litz wire 39b is twisted to form the second litz wire 39b. A litz wire 39 is formed. In this way, by increasing the number of strands 39a constituting the first litz wire 39b, the skin effect of the first litz wire itself is promoted, and the number of strands 39a is more than the number of first litz wires 39b. By increasing the number of gaps, the gap between the first litz wires can be secured a little. Therefore, by promoting the proximity effect, the skin effect and the proximity effect are both balanced.

  Further, the surface area of the induction heating coil 35 can be increased by making the wire diameter of the wire 39a as small as possible. However, if the wire 39a is too thin, the wire 39a may be disconnected. The first litz wire 39b is formed by twisting a plurality of strands 39a at a constant pitch, but the smaller the twist pitch, the more the strands 39a are not scattered, but the strand 39a is too small. Will break. For this reason, in order to configure the twist pitch as small as possible, it is necessary to increase the number of strands 39a and twist the strands 39a at a smaller pitch while preventing disconnection of the strands 39a. As described above, by increasing the number of the strands 39a constituting the first litz wire 39b, it is possible to prevent the strand 39a having a smaller wire diameter from being disconnected and to increase the surface area of the induction heating coil 35. In addition, it is possible to prevent the strands 39a of the induction heating coil 35 from being scattered and to stabilize the shape of the induction heating coil 35.

  Further, it is necessary to increase the oscillation frequency of the high-frequency current as the wire diameter of the wire 39a is reduced. Increasing the oscillation frequency also causes a switching loss of a control component for oscillating a high-frequency current. Taking the above points into consideration, the use of the wire 39a having an outer diameter of about φ0.1 prevents the wire 39a itself from being disconnected and ensures the surface area of the induction heating coil 35 while maintaining the shape stability. This is intended to improve performance and dimensional accuracy.

  In addition, as shown in FIG. 3, a ferrite 40 is installed on the outer facing portion of the induction heating coil 35. The ferrite 40 is installed radially from the central portion of the induction heating coil 35, and the shape thereof is also substantially along the pan 34 and the induction heating coil 35. The distance between the pan 34 and the induction heating coil 35 is slightly different. Although there is a difference, I try to keep it almost constant. Further, one end face of the ferrite 40 is located inside the inner diameter of the bottom induction heating coil 35a, and the other end is placed outside the outer diameter of the side induction heating coil 35b.

  Eight of these ferrites 40 are installed, and they are installed almost evenly so that the heating of the pan 34 is uniform.

  In the above description, the outer diameter, the number of core wires, and the number of the first litz wires 39b constituting the second litz wire 39 are limited, but are limited to these values. The same effect can be obtained as long as the configuration of the strands 39a and the first litz wires 39b satisfies the conditions of the present invention.

  Moreover, although the external shape of the strand 39a is also limited to φ0.1 mm, it is not limited to this value, and the same effect can be obtained if the outer diameter is φ0.1 to 0.3 mm. Further, the number of windings of the induction heating coil 35 is not limited to the above description.

  Further, the ferrite 40 covers both the bottom induction heating coil 35a and the side induction heating coil 35b with the integral ferrite 40, but it is not necessary to be integral, and each bottom induction heating coil 35a and the side induction heating coil 35b are connected to each other. By covering with separate ferrite, it is possible to obtain substantially the same effect as the integral ferrite. Further, the shape of the ferrite 40 is not limited to the shape along the shape of the induction heating coil 35. For example, a linear ferrite may be installed.

  In addition, the induction heating coil 35 is wound around the second litz wire 39 in a spiral shape, but when it is wound in a spiral shape, it is not only wound in one layer but also inducted by winding in two layers as shown in FIG. If the heating coil 35 is configured, it is possible to secure a larger number of turns than winding in one layer for the same coil width. Thus, when there is a limited condition for the width of the induction heating coil 35, the number of coil turns can be determined freely regardless of the coil width condition by winding the coil not in a single layer but in multiple layers. Moreover, by making the induction heating coil 35 into a multi-layer winding, not only can the area of the portion of the pan 34 to be heated be determined freely, but also the amount of heat generated at that portion can be determined freely, improving rice cooking performance. It can be easily realized.

  In addition, when winding in multiple layers, the direction in which the second Litz wire 39 of the second layer is placed between the second Litz wire 39 of the first layer is 2 above the second Litz wire 39 of the first layer. It goes without saying that the gap between the lines can be reduced as compared with the case where the second Litz wire 39 of the layer is installed. Therefore, when the induction heating coil 35 is wound in multiple layers, the gap can be reduced by winding the litz wire 39 of the next layer between the second litz wires 39 of the first layer.

  When the induction heating coil 35 is wound in multiple layers, the gap can be minimized by making the sectional shape of the second litz wire 39 constituting the induction heating coil 35 substantially hexagonal.

  The induction heating coil 35 is composed of a bottom induction heating coil 35a and a side induction heating coil 35b. However, when it is wound in multiple layers, it is not necessary to wind both layers in multiple layers, and only one of them is wound in multiple layers. In this way, the same effect can be obtained.

  In the present embodiment, the rice cooker has been described as an example. However, the present invention is not limited to this, and the present invention can also be applied as a device such as an IH cooker.

  As described above, the heating device according to the present invention can improve the moldability of the induction heating coil and can improve the heating efficiency as the device. It can be applied to general electromagnetic induction heating equipment.

Sectional drawing of the heating apparatus in embodiment of this invention Sectional drawing which shows the 2nd litz wire which forms the induction heating coil of the heating apparatus Bottom view showing the induction heating coil part of the same heating device Sectional drawing which shows an example of the induction heating coil structure of the heating apparatus Sectional drawing which shows the other examples of the induction heating coil structure of the heating apparatus

Explanation of symbols

31 Equipment 34 Heated object (pan)
35 Induction heating coil 35a Bottom induction heating coil 35b Side induction heating coil 39 Second litz wire 39a Wire 39b First litz wire

Claims (5)

An induction heating coil for induction heating of an object to be heated is provided, the induction heating coil twisting a plurality of first litz wires obtained by twisting a plurality of strands having an insulating layer on a conductor and a plurality of first litz wires. A heating apparatus that is formed of the combined second litz wire and has a larger number of strands constituting the first litz wire than the first litz wire number forming the second litz wire. The heating apparatus according to claim 1, wherein the induction heating coil has a spiral shape and is disposed so as to face a bottom portion of the pan and a side surface portion of the pan bottom that are to be heated. The heating apparatus according to claim 2, wherein the induction heating coil has a smaller number of turns of the induction heating coil facing the pan bottom side surface than the number of turns of the induction heating coil facing the bottom of the pan. The induction heating coil according to claim 2 or 3, wherein the induction heating coil has a thickness of the induction heating coil facing the pan bottom side portion thinner than a thickness of the induction heating coil facing the pan bottom. The heating apparatus according to any one of claims 2 to 4, wherein the induction heating coil is formed in a spiral shape by overlapping a plurality of stages.